The German Patent Application DE 103 51 202 A1 describes a device for adjusting guide vanes of a gas turbine, where guide vanes are pivotably coupled by actuating levers to an actuating ring, all guide vanes of the same guide vane ring being uniformly pivotable by the actuating ring.
The U.S. Patent Application 2015/0159551 A1 discusses a guide vane ring having variable guide vanes; in the circumferential direction, two guide vanes having a different spacing than the other guide vanes (“cyclic spacing”).